We observed G 9-40 with the InfraRed Doppler instrument [1]}, [2]} behind an AO system [3]} on the Subaru 8.2-m telescope on Mauna Kea Observatories, as part of the open-use programs for following up transiting planet
candidates (S18B-114 and S19A–069I).
We took a total of 13 spectra between January 2019 and April 2021, simultaneously with laser-frequency comb spectra.
Exposure times were typically 600-1200 s and the S/N at \({1.0}{}\)  was between 60–80 per spectral bin. We reduced the raw IRD frames of G 9-40 using the Échelle package of iraf for flat-fielding, scattered-light subtraction, aperture tracing, and wavelength calibration with the Th-Ar lamp spectra. For a more precise wavelength calibration, the wavelength was re-calibrated based on the emission lines of the combined laser frequency comb, which was injected simultaneously into both stellar and reference fibres during instrument calibrations. We injected these reduced spectra into the RV analysis pipeline for Subaru/IRD [4]} and attempted to reproduce the intrinsic stellar template spectrum from all the observed spectra with instrumental profile deconvolution and telluric removal. RVs were measured with respect to that template by forward-modeling of the observed individual spectral segments (each spanning 0.7–1.0 nm). The uncertainties of the measured RVs are in the range 3.1–6.8 \(\mathrm {m\,s^{-1}}\)  with a mean value of 4.5 \(\mathrm {m\,s^{-1}}\) .
